This proposal extends the use of a laboratory methodology developed for the study of sensory processes in non-human primates to the analysis of the effects of known drugs of abuse upon 1) sensory function as indicated by absolute thresholds to auditory and visual stimuli in baboons, and 2) motor function as indicated by measured reaction times to these auditory and visual stimuli. Initial objectives of the research focus upon the validity, reliability, sensitivity, and selectivity of the psychophysical procedures for evaluating such effects. Secondly, a series of experiments will be carried out with the objective of characterizing and comparing a range of abuseable drugs, doses, and drug classes with respect to their effects upon auditory and visual threshold sensitivity and reaction time performance. Those pharmacologic compounds to be examined include prototypic barbiturates, benzodiazepines, opiates, stimulants, and hallucinogens. The procedure of choice is the reaction time procedure in which unrestrained baboons press and hold down a lever until an auditory or visual stimulus occurs, signalling reward availability contingent upon rapid release of the lever. Testing begins after drug administration, with stimulus intensity randomly varied during each session to determine sensory thresholds.